从 Flask 视图创建和下载 CSV 文件

Question

我试图让用户下载一个 CSV 文件，其中包含由他们的操作定义的数据。该文件不存在，它是动态创建的。我如何在 Flask 中执行此操作？

Answer 1

使用 csv.writer and stream the response. Use StringIO 生成数据以写入内存缓冲区而不是生成中间文件。

import csv
from datetime import datetime
from io import StringIO
from flask import Flask
from werkzeug.wrappers import Response

app = Flask(__name__)

# example data, this could come from wherever you are storing logs
log = [
    ('login', datetime(2015, 1, 10, 5, 30)),
    ('deposit', datetime(2015, 1, 10, 5, 35)),
    ('order', datetime(2015, 1, 10, 5, 50)),
    ('withdraw', datetime(2015, 1, 10, 6, 10)),
    ('logout', datetime(2015, 1, 10, 6, 15))
]

@app.route('/')
def download_log():
    def generate():
        data = StringIO()
        w = csv.writer(data)

        # write header
        w.writerow(('action', 'timestamp'))
        yield data.getvalue()
        data.seek(0)
        data.truncate(0)

        # write each log item
        for item in log:
            w.writerow((
                item[0],
                item[1].isoformat()  # format datetime as string
            ))
            yield data.getvalue()
            data.seek(0)
            data.truncate(0)

    # stream the response as the data is generated
    response = Response(generate(), mimetype='text/csv')
    # add a filename
    response.headers.set("Content-Disposition", "attachment", filename="log.csv")
    return response

如果generate函数需要来自当前request的信息，它应该用stream_with_context装饰，否则你会得到"working outside request context"错误。其他一切都保持不变。

from flask import stream_with context

@stream_with_context
def generate():
    ...

Answer 2

Flask-Excel 库使用 PyExcel 生成 CSV 或其他电子表格格式并生成 Flask 响应。文档列出了如何生成其他格式以及可以使用哪些数据的完整 API。

pip install flask-excel

import flask_excel as excel

@app.route('/download', methods=['GET'])
def download_data():
    sample_data=[0, 1, 2]
    excel.init_excel(app)
    extension_type = "csv"
    filename = "test123" + "." extension_type
    d = {'colName': sample_data}
    return excel.make_response_from_dict(d, file_type=extension_type, file_name=filename)

从 Flask 视图创建和下载 CSV 文件

Create and download a CSV file from a Flask view

python

csv

flask